Answer:
(c) 16 m/s²
Explanation:
The position is ![r(t) = [3.0 \text{ m} - (4.00 \text{ m/s})t]\hat{i} + [6.0 \text{m} - (8.00 \text{ m/s}^2 )t^2 ]\hat{j}](https://tex.z-dn.net/?f=r%28t%29%20%3D%20%5B3.0%20%5Ctext%7B%20m%7D%20-%20%284.00%20%5Ctext%7B%20m%2Fs%7D%29t%5D%5Chat%7Bi%7D%20%2B%20%5B6.0%20%5Ctext%7Bm%7D%20-%20%288.00%20%5Ctext%7B%20m%2Fs%7D%5E2%20%29t%5E2%20%5D%5Chat%7Bj%7D)
.
The velocity is the first time-derivative of <em>r(t).</em>
<em />
<em />
The acceleration is the first time-derivative of the velocity.
Since <em>a(t)</em> does not have the variable <em>t</em>, it is constant. Hence, at any time,
Its magnitude is 16 m/s².
Answer:
Microwave: Radiation
Water: Conduction, convection & radiation.
Explanation:
- When we heat a food using microwave then the water content of the food is only heated by the microwave.
- Microwaves make the molecules of water vibrate frequently with a frequency closer to the frequency of microwaves and this increases the kinetic energy of the molecules which produces heat in the water molecules this heat then propagates to the whole food by conduction and convection, but the heat enters the food only via radiation.
Now when the food item is kept into warm water then the molecules closer to the food heat the food by conduction through direct energy transfer by lattice vibrations and when they become cooler than the mass of water all around then due to density difference they settle down and their place is occupied by warmer molecules around in the fluid leading to convection.
Radiation of energy from a mass occurs continuously irrespective of the medium present there. So the heat of water also enters the food by radiation of energy from the water molecules.
The car undergoes an acceleration <em>a</em> such that
(45.0 km/h)² - 0² = 2 <em>a</em> (90 m)
90 m = 0.09 km, so
(45.0 km/h)² - 0² = 2 <em>a</em> (0.09 km)
Solve for <em>a</em> :
<em>a</em> = (45.0 km/h)² / (2 (0.09 km)) = 11,250 km/h²
Ignoring friction, the net force acting on the car points in the direction of its movement (it's also pulled down by gravity, but the ground pushes back up). Newton's second law then says that the net force <em>F</em> is equal to the mass <em>m</em> times the acceleration <em>a</em>, so that
<em>F</em> = (4500 kg) (11,250 km/h²)
Recall that Newtons (N) are measured as
1 N = 1 kg • m/s²
so we should convert everything accordingly:
11,250 km/h² = (11,250 km/h²) (1000 m/km) (1/3600 h/s)² ≈ 0.868 m/s²
Then the force is
<em>F</em> = (4500 kg) (0.868 m/s²) = 3906.25 N ≈ 3900 N
Answer: vibrate
Explanation:
The object in air can be particular objects or substances.
Sound is actually vibration of waves through a medium. The medium can be liquid, solid or gas.
Therefore, the one word that will complete and make the sentence to make sense is ' vibrate '
